Duplex - Cisco Catalyst 3750-X Command Reference Manual

duplex

duplex
Use the duplex interface configuration command on the switch stack or on a standalone switch to specify
the duplex mode of operation for a port. Use the no form of this command to return the port to its default
value.
Syntax Description
auto
full
half
Defaults
The default is auto for Gigabit Ethernet ports.
You cannot configure the duplex mode on 10-Gigabit Ethernet ports; it is always full.
Duplex options are not supported on the 1000BASE-x (where -x is -BX, -CWDM, -LX, -SX, or -ZX)
SFP modules.
The default is half for 100BASE-x (where -x is -BX, -FX, -FX-FE, or - LX) small form-factor pluggable
(SFP) modules.
For information about which SFP modules are supported on your switch, see the product release notes.
Command Modes Interface configuration
Command History Release
12.2(53)SE2
Usage Guidelines
For Fast Ethernet ports on stack members other than Catalyst 3750-X switches, setting the port to auto
has the same effect as specifying half if the attached device does not autonegotiate the duplex parameter.
For Gigabit Ethernet ports, setting the port to auto has the same effect as specifying full if the attached
device does not autonegotiate the duplex parameter.
Note
Certain ports can be configured to be either full duplex or half duplex. Applicability of this command
depends on the device to which the switch is attached.
Catalyst 3750-X and 3560-X Switch Command Reference
2-210
duplex {auto | full | half}
no duplex
Enable automatic duplex configuration; port automatically detects whether it
should run in full- or half-duplex mode, depending on the attached device mode.
Enable full-duplex mode.
Enable half-duplex mode (only for interfaces operating at 10 or 100 Mb/s). You
cannot configure half-duplex mode for interfaces operating at 1000 or
10,000 Mb/s.
Modification
This command was introduced.
Half-duplex mode is supported on Gigabit Ethernet interfaces if the duplex mode is auto and the
connected device is operating at half duplex. However, you cannot configure these interfaces to
operate in half-duplex mode.
Chapter 2 Catalyst 3750-X and 3560-X Switch Cisco IOS Commands
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